1. Field of the Invention
The present invention relates to a format converting apparatus and more particularly to a format converting apparatus for exchanging data between a serial bus and a remodulator.
2. Discussion of Related Art
An Institute of Electrical and Electronics Engineers (IEEE) 1394 is one of the standards for a digital interface allowing a mutual connection between equipments. The IEEE 1394 provides a transmission technique or standard between digital equipments as developed by U.S.A. Apple Co. The IEEE 1394 also provides a new interface standard in which multimedia data can be transmitted and received at a high speed of 100 Mbpsxcx9c1 Gbps by connecting communication instruments, computers and household electric appliances through a single network.
The IEEE 1394 is based on a remarkable bilateral nature and is recognized as a technique capable of leading the age of multimedia. Especially, the IEEE 1394 supports both an asynchronous transmission such as a printer or scanner which does not require a real time operation, and an isochronous transmission such as a motional image or sound which requires a real time operation. The IEEE 1394 also has a characteristic of transmitting data rapidly and with stability by connecting only one cable in series to a personal computer (PC), regardless of a size or number of peripheral equipments. Accordingly, the development of products and parts for computers and household electric appliances have been accelerated.
FIG. 1 is a block diagram of a conventional digital broadcasting receiver utilizing the IEEE 1394. Referring to FIG. 1, a wireless signal is input through an antenna and is converted into a transport stream in a tuner and error corrector 101. After an error correction, the signal is output to a transport inverse multiplexer (MUX) 104. The transport stream inverse multiplexed into an audio and video (A/V) packetized elementary streams (PES) by the transport inverse MUX 104. A Moving Picture Experts Group Audio/Video (MPEG A/V) decoder 105 receives and decompresses the A/V PES. A NTSC/PAL encoder 106 converts the decompressed A/V data into an NTSC or PAL format and outputs the data to a TV or a video cassette recorder (VCR). A controller 100 controls the blocks above and performs functions such as a channel conversion according to inputs from a user. Such digital broadcasting receiver can selectively include one of an IEEE 1394 port 102 or a VSB-R port 103, or can include both.
The IEEE 1394 port 102 is defined by the standard of an IEEE standard 1394-1995 serial bus, and is embodied by implementing IEEE 1394 physical and link layers. As shown in FIG. 1, the IEEE 1394 port 102 is connected to the transport inverse MUX 104 and transmits the transport stream externally or outputs the externally received transport stream to the transport inverse MUX 104. The VSB-R port 103 is based on a data transmission system defined by the standard of an EIA-762 and EIA-761, and is embodied by implementing a VSB-R. The VSB-R port 103 is also connected to the transport inverse MUX 104 to transmit or receive the transport stream.
FIG. 2 shows a block diagram of the IEEE 1394 physical and link layers (PHY and LINK layers) including a host processor 201 as a controller, a link layer 202, a physical layer 203 and an IEEE 1394 cable. The IEEE 1394 cable is provided as a physical unit used for forming a bus to exterior equipments. The physical layer 203 is connected to the IEEE 1394 bus utilizing the IEEE 1394 cable, loads transmission digital data on the IEEE 1394 bus and extracts data from the IEEE 1394 bus.
The digital data transferred by the bus is classified into either an isochronous data or an asynchronous data depending upon its attribute. The isochronous data is transferred through an isochronous channel by a constant transmission rate to ensure a real time transmission. The asynchronous data is transferred through an asynchronous channel and is particularly transmitted intermittently utilizing a spare bandwidth of the bus. In general the isochronous channel has a high data rate like the transport stream and is used for transmitting data necessary for a real time transmission, and the asynchronous channel is used for transmitting and receiving a control command between equipments.
The link layer 202 multiplexes the isochronous channel and the asynchronous channel so that the host processor 201 can separate the data into isochronous and asynchronous data to process the data. The host processor 201 controls the link layer 202 to transmit and receive the isochronous and asynchronous data. The IEEE 1394 can also be implemented as a network between the equipments.
FIG. 3 is an example of a network utilizing the IEEE 1394 serial bus. For example, a digitized sound is transmitted as an isochronous data from a magnetic disk to a stereo interface, and a video image is transmitted as an isochronous data from a digital camera to a central process unit (CPU). Thus, two isochronous data are simultaneously transmitted between the stereo interface and the CPU. Such operation is available because the IEEE 1394 bus performs a multiplexation on the isochronous and asynchronous channels in a time-division multiplex structure as shown in FIG. 4.
The multiplexation in FIG. 4 is performed in cycles of 125 xcexcs. Within each cycle, the isochronous channels must be transmitted according to a order of priority, and the asynchronous packets are transmitted in the remaining time.
FIG. 5 is a block diagram of a typical VSB-R 102. A transport stream, ATSC MPEG-2 data packet, is input and stored in a buffer 501. The input transport stream is then transmitted to a remodulator 502 at a necessary point in time. The remodulator 502 performs a radio frequency (RF) modulation based on an 8 VSB or a 16 VSB system as defined in the ATSC standard A/53 annex D. Thus, the remodulator 502 receives data from the buffer 501 and executes the VSB modulation. The VSB modulated transport stream input at this time may be multiplexed with an On Screen Display (OSD) data.
FIG. 6 shows a multiplexation structure of the OSD data defined in the VSB-R standard. The OSD data includes an OSD header and OSD data. Namely, the OSD header stores data such as a start position and size information of an OSD area, and palette information usable within the area. The OSD data stores bitmap information for all pixels provided within the OSD area. Thus the OSD data is converted into a packetized structure defined in the MPEG-2 standard. In other words, the OSD data is first packetized into a PES, and then re-packetized into a transport packet. Therefore, the OSD data is converted into a transport stream in two steps.
However, the digital apparatus of the future may require a several number of interface standards at the same time. As an example, the digital transmission standards of the IEEE 1394 and the VSB-R may be used in a digital broadcasting receiver as shown in FIG. 1. In such case, it is currently impossible to perform a data exchange between the IEEE 1394 and the VSB-R. Namely, data input through the IEEE 1394 cannot be output through the VSB-R, and vice versa. This incompatibility is largely caused by different data transmission speed of the IEEE 1394 (200 Mbps) and the VSB-R (38.8 Mbps) and is also caused by different OSD transmission systems, thereby making it difficult to directly exchange data.
Therefore, when the IEEE 1394 and the VSB-R are both implemented within one digital apparatus, data cannot be transmitted from the IEEE 1394 to an equipment connected to the VSB-R, or vice versa.
Accordingly, an object of the present invention is to solve at least the problems and disadvantages of the related art.
An object of the present invention is to provide a format converting apparatus capable of converting a format of input data to allow exchange of data between an IEEE 1394 serial bus and a VSB-R.
Another object of the present invention is to provide a format converting apparatus capable of converting data based on a format of the IEEE 1394 into a format appropriate for the VSB-R.
A further object of the present invention is to provide a format converting apparatus capable of converting data of the VSB-R format into a format proper for the IEEE 1394.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
To achieve the objects and in accordance with the purposes of the invention, as embodied and broadly described herein, a format converting apparatus is characterized by the selecting the isochronous and asynchronous channels from the received IEEE 1394 channels, extracting OSD information from the selected asynchronous channel and converting the information into an OSD transport stream format of a VSB-R standard, and multiplexing and transmitting an A/V transport stream included in the selected isochronous channel and the converted OSD transport stream to the VSB-R.
In the format converting apparatus, the data rates from the multiplexation of the A/V and the OSD transport streams are calculated. The result of the calculation is compared with a transmission bandwidth of the VSB-R. Thus, the data rates of the A/V transport stream and the OSD transport stream are lessened or increased according to the comparison result, and thereafter, the A/V and OSD transport streams are multiplexed.
The present format converting apparatus is further characterized by receiving an isochronous channel necessary for a transmission allocated by an IEEE 1394 serial bus, performing an inverse multiplexation of the output from the VSB-R and transmitting a separated A/V transport stream through the allocated isochronous channel, and converting the OSD transport stream into an asynchronous packet according to the standard of the IEEE 1394 and transmitting the packet through the asynchronous channel.
The format converting apparatus according to the present invention can be implemented in a digital equipment having both an IEEE 1394 and a VSB-R. Particularly, the present format converting apparatus can be implemented in a digital broadcasting receiver having both an IEEE 1394 and a VSB-R.